Epoxy resin composition for FRP, prepreg, and tubular molding produced therefrom

ABSTRACT

The present invention relates to an epoxy resin composition for FRP that will be used for fishing rods, golf club shafts, and the like, a prepreg that is an intermediate material made up of an epoxy resin composition combined with reinforcing fibers, and a tubular molded article obtained using it. The epoxy resin composition for FRP of the present invention comprises (A) a bisphenol A-type epoxy resin, (B) an epoxy resin having oxazolidone rings, and (C) a curing agent. By using the epoxy resin composition for FRP of the present invention, a prepreg quite excellent in handleability and a tubular molded article improved in flexural strength in the longitudinal direction and crushing strength in the diametrical direction can be obtained.

TECHNICAL FIELD

The present invention relates to an epoxy resin composition for fiberreinforced plastics (abbreviated to FRP in this specification), aprepreg that is an intermediate material made up of a combination of anepoxy resin composition and reinforcing fibers, and a tubular moldedarticle obtained by the use thereof.

This application is based on a patent application in Japan (JapanesePatent Application No. Hei 9-74794) and the contents described in thatJapanese application are taken as part of this description.

BACKGROUND ART

Since epoxy resins after curing are excellent in mechanical properties,electrical properties, and adhesive properties, they are widely used inthe fields, for example, of sealants for electronic materials, paints,coating materials, and adhesives. Further, epoxy resins are important asmatrix resins for FRP. Particularly, when carbon fibers are used asreinforcing fibers for FRP, epoxy resins are preferably used since theyare excellent in adhesion to carbon fibers. FRP molded articles made upof carbon fibers and epoxy resins are used in wide range of applicationsranging from general-purpose use in fishing rods, golf club shafts, etc.to the use in airplanes.

The method for molding FRP molded articles from reinforcing fibers, suchas carbon fibers, and a matrix resin, such as an epoxy resin, includesseveral methods. If carbon fibers are used as reinforcing fibers, amethod wherein an intermediate material called a prepreg prepared byimpregnating in advance the reinforcing fibers with a resin is used forthe molding of an FRP molded article is most widely used. The matrixresin used in this prepreg is required to be excellent, for example, inadhesion to the reinforcing fibers and mechanical properties after themolding. Further, the prepreg is required to have suitable tack in orderto make the handling good. Since epoxy resins can be made to exhibitrelatively easily these properties in a well balanced manner, they arewidely used as a matrix resin for prepregs.

The major application of these FRP molded articles includes tubularmolded articles, such as fishing rods and golf club shafts. Such tubularmolded articles are required to have, as important properties, flexuralstrength in the longitudinal direction and crushing strength in thediametrical direction.

In order to enhance the flexural strength of tubular molded articles inthe longitudinal direction, it is already known that it is effective toarrange carbon fibers along the length. Further, in order to improve thecrushing strength of tubular molded article in the diametricaldirection, it is already known that it is effective to arrange carbonfibers circumferentially. However, when a tubular molded article isreinforced longitudinally and circumferentially at the same time, thetubular molded article inevitably increases in weight. An increase inweight of a tubular molded article runs counter to the recent trendwherein fishing rods and golf club shafts are made light in weight.Accordingly, there have been attempted to improve matrix resins toreduce the circumferential reinforcement of tubular molded articles.However, matrix resins that can make tubular molded articles light inweight are not now available.

The present invention aims at providing an epoxy resin composition forFRP in order to obtain tubular molded articles improved in flexuralstrength in the longitudinal direction and crushing strength in thediametrical direction and a prepreg made of a combination of that epoxyresin composition for FRP and reinforcing fibers.

DISCLOSURE OF THE INVENTION

The first subject matter of the present invention resides in an epoxyresin composition for FRP, characterized in that it comprises (A) abisphenol A-type epoxy resin (hereinafter referred to as component (A)),(B) an epoxy resin having oxazolidone rings represented by (hereinafterreferred to as component (B)), and (C) a curing agent (hereinafterreferred to as component (C)), the component (B) is an epoxy resinhaving a structure represented by the following formula (1):

wherein R represents a hydrogen atom or a methyl group, and theviscosity measured by the below-described method for measuringviscosities is 100 to 5,000 poises.

Method for Measuring Viscosities

Use is made of a dynamic viscoelasticity measuring instrument, theuncured epoxy resin composition for FRP whose viscosity will be measuredis filled between two disk plates 25 mm in diameter that are positionedwith a space of 0.5 mm between them, one of the disk plates is rotatedat a shear rate of 10 radians/sec, and the viscosity of the epoxy resinis measured under conditions in which the atmospheric temperature forthe measurement is 60° C.

The second subject matter resides in an epoxy resin composition for FRP,characterized in that it comprises a component (A), a component (B), anda component (C), and (D) a thermoplastic resin that can be dissolved ina mixture of the component (A) and the component (B) (hereinafterreferred to as component (D)) and has a viscosity of 100 to 5,000 poisesmeasured by the above method.

Further, the third subject matter resides in a prepreg comprising asheet of reinforcing fibers impregnated with the above epoxy resincomposition for FRP.

Further the fourth subject matter resides in a tubular molded articlehaving a plurality of FRP layers, characterized in that the matrix resincomposition used in at least one of the FRP layers is the above epoxyresin composition for FRP.

And the fifth subject matter resides in an epoxy resin composition forFRP, characterized in that when the epoxy resin composition for FRP ismolded into a tubular product, the crushing strength is 200 N or more.

In the present invention, “crushing strength” means the crushingstrength, measured by the below-described method, of a tubular moldedarticle that has an inner diameter of 10 mm, an outer diameter of 12 mm,and a volume content of fibers of 60+1% and is prepared by impregnatingcarbon fibers having an elastic modulus of 220 to 250 GPa with the epoxyresin composition for FRP to make unidirectional prepregs wherein thecarbon fiber areal weight is 150 g/m² and the content of the epoxy resinfor FRP is 31% by weight and laminating the unidirectional prepregs sothat the directions of the fibers may be +45°/−45°/+45°/−45°/0°/0°/0°.

Method for Measuring Crushing Strength

The above-described tubular molded article is cut into a length of 10 mmto obtain a test piece. Using an indenter, a load is exerted on the testpiece and the maximum load at which the test piece is broken when theindenter is moved at a rate of travel of 5 mm/min is measured and isdesignated as the crushing strength.

Further, the sixth subject matter resides in an epoxy resin compositionfor FRP, characterized in that when the epoxy resin composition for FRPis made into a unidirectional laminate, the flexural strength in adirection of 90° is 110 MPa or more.

In the present invention, “flexural strength in a direction of 90°”means the flexural strength of 90°, measured by the below-describedmethod, of the unidirectional laminate that is prepared by impregnatingcarbon fibers having an elastic modulus of 220 to 250 GPa with the epoxyresin composition for FRP to make unidirectional prepregs wherein thecarbon fiber areal weight is 150 g/m² and the content of the epoxy resinfor FRP is 31% by weight and laminating fifteen unidirectional prepregsthus made (2 mm in thickness) so that the directions of the fibers maybe 0 degrees.

Method for Measuring Flexural Strength in a Direction of 90°

The above-described unidirectional laminate is cut to obtain a testpiece having a length of 60 mm in a direction of 90° to the direction ofthe fibers and a width of 10 mm. The maximum load when the test piece isbroken is measured under conditions wherein the distance between thesupports is 32 mm, the diameter of the tip of the indenter is 3.2 mm,and the rate of travel of the indenter is 2 mm/min and the flexuralstrength is calculated.

Best Mode for Carrying Out the Invention

As the component (A) of the epoxy resin composition for FRP of thepresent invention, those which are generally on the market can be used.As the component (A), those which when used in the epoxy resincomposition for FRP bring its viscosity to the range described later maybe used. The epoxy equivalent, the molecular weight, and the state atnormal temperatures of the component (A) are not particularlyrestricted. Herein, “epoxy equivalent” in the present invention meansthe number of grams of the resin containing epoxy groups in an amount of1 gram equivalent. As the component (A), a mixture of a bisphenol A-typeepoxy resin having an epoxy equivalent of 300 or less that is a liquidor a semisolid at normal temperatures and a bisphenol A-type epoxy resinhaving an epoxy equivalent of 400 or more that is a solid at normaltemperatures is preferably used because the strength in a direction of90° to the direction of fibers can be exhibited. Further, particularlypreferably, the bisphenol A-type epoxy resin having an epoxy resinequivalent of 300 or less is contained in an amount of 25 to 65% byweight in the component (A).

As typical ones of the bisphenol A-type epoxy resin having an epoxyequivalent of 300 or less that is a liquid or a semisolid at normaltemperatures, EPIKOTE 828 and EPIKOTE 834 manufactured by Yuka ShellEpoxy K. K. can be mentioned by way of example.

As representative examples of the bisphenol A-type epoxy resin having anepoxy equivalent of 400 or more that is a solid at normal temperatures,EPIKOTE 1001, EPIKOTE 1002, EPIKOTE 1004, EPIKOTE 1007, and EPIKOTE 1009can be mentioned by way of example.

As the component (B) of the epoxy resin composition for FRP of thepresent invention, an epoxy resin having oxazolidone rings representedby the below-shown formula (1) is used. This component (B) is anessential component for the purpose of the present invention forobtaining a tubular molded article that exhibits a high crushingstrength. An epoxy resin composition for FRP that does not contain thiscomponent (B) can provide neither a tubular molded article having both ahigh crushing strength and a high flexural strength nor a prepreg goodin handleability. Further it is also necessary to use an epoxy resincontaining oxazolidone rings and epoxy groups in the molecule. A mixtureof a compound containing oxazolidone rings and a compound containingepoxy groups can provide neither a tubular molded article having both ahigh crushing strength and a high flexural strength nor a prepreg goodin handleability.

wherein R represents a hydrogen atom or a methyl group.

As the component (B), an epoxy resin having a structure represented bythe below-shown formula (2) is particularly preferable. This component(B) can be synthesized by a method disclosed in Japanese PatentApplication, First Publication No. Hei 5-43655 wherein an epoxy resinand an isocyanate compound are reacted in the presence of an oxazolidonering forming catalyst. Further, as commercially available epoxy resinsthat can be used as the component (B), XAC4151 and XAC4152 manufacturedby Asahi-Ciba Limited can be mentioned by way of example.

wherein R's each independently represent a hydrogen atom or a methylgroup, R₁ to R₄ each independently represent a halogen atom, a hydrogenatom, or an alkyl group having 1 to 4 carbon atoms, R₅ to R₈ eachindependently represent a hydrogen atom or an alkyl group having 1 to 4carbon atoms, and R₉ has the below-shown formula (3) or the below-shownformula (4).

wherein R′₁ to R′₄ each independently represent a hydrogen atom or analkyl group having 1 to 4 carbon atoms.

wherein R′₁ to R′₈ each independently represent a hydrogen atom or analkyl group having 1 to 4 carbon atoms and R′₉ represents a single bond,—CH₂—, —C(CH₃)₂—, —SO₂—, —SO—, —S—, or —O—.

As the component (C) of the epoxy resin composition for FRP of thepresent invention, any curing agent can be used that is used as a curingagent for usual epoxy resin compositions. As typical curing agents,dicyandiamides, ureacompounds, amine compounds, acid anhydrides,imidazole compounds, phenol compounds, etc. can be mentioned by way ofexample. Among others, a combination of a dicyandiamide and a ureaseries compound is particularly preferable because the curability of theepoxy resin composition for FRP and the balance among the physicalproperties of the molded article obtained after the curing are good.

To the epoxy resin composition for FRP of the present invention, thecomponent (D) can be added. By adding the component (D) to the epoxyresin composition for FRP, the handleability of the prepreg is furtherimproved and the properties of the obtainable tubular molded article,such as the crushing strength, are improved and stabilized.

As the component (D) of the epoxy resin composition for FRP of thepresent invention, a thermoplastic resin that dissolves uniformly in amixture of the component (A) with the component (B) is used. As thecomponent (D), phenoxy resins and polyvinylformal resins areparticularly preferably used. The phenoxy resins are not particularlyrestricted and those generally on the market can be used. For example,PHENOTOHTO YP-50 and PKHP-200 manufactured by Tohto Kasei Co., Ltd. etc.can be mentioned as typical examples thereof. As the polyvinylformalresin (hereinafter referred to as PVF), a resin containing 60% by weightor more of a vinyl formal moiety with the rest made up of vinylalcohol,vinylacetate, or the like is used. VINYLEC manufactured by ChissoCorporation can be mentioned as commercially available typical examplesthereof.

The epoxy resin composition for FRP of the present invention is requiredto have a viscosity of 100 to 5,000 poises measured by thebelow-described method for measuring viscosities. If the viscosity ofthe epoxy resin composition for FRP is less than 100 poises at 60° C.,the tack becomes too strong or the resin flow at the time of moldingbecomes too great, making it impossible to obtain the intendedproperties after the molding, which is unpreferable. Furthermore, if theviscosity of the epoxy resin composition for FRP is over 5,000 poises,the impregnation with the resin at the time of formation of a prepregbecomes insufficient, the tack is lost to too great an extent, or theprepreg becomes hard, making it impossible to obtain the intendedproperties after the molding, which is unpreferable. A more preferablerange is from 300 to 3,000 poises.

The viscosity in the present invention is the viscosity measured byusing a dynamic viscoelasticity measuring instrument, such as a dynamicviscoelasticity measuring instrument RDA-700 manufactured by RheometricScientific F. E. Ltd. in such a manner that the uncured epoxy resincomposition for FRP whose viscosity will be measured is filled betweentwo disk plates which are 25 mm in diameter that are positioned with aspace of 0.5 mm between them, one of the disk plates is rotated at ashear rate of 10 radians/sec, and the viscosity of the epoxy resin ismeasured under conditions in which the atmospheric temperature for themeasurement is 60° C.

The formulation ratio of the components in the epoxy resin compositionfor FRP of the present invention is not particularly restricted so longas the composition satisfies the above conditions including theviscosity conditions. If the component (D) is not contained, theformulation ratio [(A)/(B)] of the component (A) and the component (B)is preferably in the range of from 9/1 to 3/7 by weight. Further,particularly preferably, the component (B) accounts for 20 to 50% byweight of the mixture of the component (A) and the component (B).

Further, when the component (D) is contained, the formulation ratio[(A)/(B)] of the component (A) and the component (B) is preferably inthe range of from 15/1 to 1/5 by weight and more preferably in the rangeof from 10/1 to 1/3 by weight. Further, most preferably, the component(B) accounts for 7 to 50% by weight of the mixture of the component (A)and the component (B).

When only a phenoxy resin is used as the component (D) of the epoxyresin composition for FRP of the present invention, the formulationratio {(D)/[(A)+(B)]} of the components in the epoxy resin compositionfor FRP is preferably in the range of from 1/100 to 30/100 by weight andmore preferably in the range of from 2/100 to 20/100 by weight. Further,when only a polyvinylformal resin is used as the component (D), theformulation ratio {(D)/[(A)+(B)]} of the components in the epoxy resincomposition for FRP is preferably in the range of from 1/100 to 20/100and more preferably in the range of from 1/100 to 10/100.

To the epoxy resin composition for FRP of the present invention, anotherepoxy resin (E) (hereinafter referred to as component (E)) can be addedin the range wherein the above formulation ratios are satisfied. Byadding the component (E) to the epoxy resin composition for FRP, theproperties of the tubular molded article, such as the heat resistance,can further be improved.

As the component (E),. for example, bisphenol F-type, bisphenol S-type,glycidylamine-type, aminophenol-type, phenolic novolak- type, and cresolnovolak-type epoxy resins, or aliphatic, cycloaliphatic, and other epoxyresins can be mentioned. Among others, phenolic novolak-type epoxyresins having a softening point of 60° C. or more are particularlypreferable because they less adversely affect the balance of the entireproperties of the epoxy resin composition for FRP. As typical examplesof phenolic novolak-type epoxy resins having a softening point of 60° C.or more, EPICLON N-770 and N-775 manufactured by Dainippon Ink andChemicals Inc. can be mentioned.

When the component (E) is added to the epoxy resin composition for FRP,the component (E) is contained in an amount of 3 to 20% by weight basedon the total of the epoxy resin components consisting of the component(A), the component (B) and the component (E). Further, more preferably,the total amount of the component (B) added and the amount of thecomponent (E) added is 20 to 50% by weight based on the total of theepoxy resin components consisting of the component (A), the component(B), and the component (E), and the composition ratio of the component(B) to the composition (E) is in the range of from 1/3 to 4/1.

As the epoxy resin composition for FRP of the present invention, thosethat are excellent in toughness in addition to the above conditions aremore preferable. Specifically, an epoxy resin composition for FRP whoseG_(IC) (critical strain energy release rate) is 400 J/m² or more isparticularly preferable. Herein, G_(IC) can be measured by the compacttension method described in ASTM-E399.

A sheet of reinforcing fibers is impregnated with the epoxy resincomposition for FRP of the present invention to make them integrated,thereby forming an intermediate material called a prepreg.

The reinforcing fibers used in the present invention are notparticularly restricted and use is made of carbon fibers, glass fibers,aramid fibers, boron fibers, steel fibers, etc. singly or incombination. Among others, carbon fibers are particularly preferablyused since the mechanical properties after molding are good.

As the carbon fibers, any of PAN precursor carbon fibers and pitchprecursor carbon fibers can be used. Further, as the carbon fibers,various carbon fibers different in strength and elastic modulus can beselected and used according to the purpose.

Further, as the prepreg of the present invention, for example, aunidirectional prepreg wherein reinforcing fibers are arranged in onedirection, a fabric wherein reinforcing fibers are woven, a nonwovenfabric of reinforcing fibers, or a prepreg prepared by impregnating atow of reinforcing fibers directly with the epoxy resin composition forFRP of the present invention can be mentioned.

In the present invention, the sheetlike product wherein reinforcingfibers are arranged in one direction, the fabric wherein reinforcingfibers are woven, the nonwoven fabric made up of reinforcing fibers, thetow of reinforcing fibers, and the like are simply referred to as asheet of reinforcing fibers.

The method for impregnating reinforcing fibers with the epoxy resincomposition for FRP of the present invention is not particularlyrestricted. As the method for impregnating reinforcing fibers with theepoxy resin composition for FRP, a method wherein a sheet of reinforcingfibers is impregnated with the resin from both surfaces thereof ispreferred over a method wherein a sheet of reinforcing fibers isimpregnated with the resin from one surface thereof because, in theformer case, when the sheet is molded into the tubular molded articleintended by the present invention, the crushing strength and theflexural strength in a direction of 90° are improved.

When the epoxy resin composition for FRP of the present invention ismade into a prepreg, the prepreg has suitable tack and flexibility andis good in the balance between stability with time and curability. Inparticular, when the epoxy resin composition for FRP of the presentinvention is made into a unidirectional prepreg of carbon fibers, suchan effect is brought about that the flexural strength in a direction of90° to the axes of the fibers of the molded article is considerablyimproved. As a result, the tubular molded article obtained by using theprepreg is improved considerably in crushing strength and flexuralstrength. Such an effect is difficult to obtain using conventionalmatrix resins and thus reflects the excellent performance of the epoxyresin composition of the present invention.

In particular, when a prepreg having a flexural strength of 125 MPa ormore in a direction of 90° to the axes of the fibers is used, thecrushing strength of the obtained tubular molded article is remarkablyimproved. Thus, the crushing strength is greatly affected by flexuralstrength in a direction of 90° to the axes of the fibers. Further, theeffect of the elastic modulus of the carbon fibers used is also greatand when carbon fibers having a high elastic modulus are used, generallya favorable crushing strength is readily be obtained.

Accordingly, when carbon fibers having a high elastic modulus are used,a good crushing strength is obtained even when the flexural strength ina direction of 90° to the axes of the carbon fibers is a little low. Inparticular, a good crushing strength is obtained in the case in whichthe flexural strength in a direction of 90° to the axes of the fibersand the elastic modulus of the carbon fibers used satisfy the followingrelationship:

flexural strength in a direction of 90° [MPa]≧2,500/the elastic modulusof the carbon fibers [GPa]

On the other hand, the lower the resin content in the prepreg is, thebetter it is, since the tubular molded article is made lighter inweight. However, a decrease in the resin content is apt to result inlowering of the flexural strength in a direction of 90° to the axes ofthe fibers. Particularly, in the case in which the resin content is lessthan 25% by weight, the tendency for the lowering thereof is increased.Therefore, when a conventional epoxy resin composition was used as amatrix resin, it was difficult to secure sufficient crushing strengthwith the resin content of the prepreg lowered to make the tubular moldedarticle light in weight. However, when the epoxy resin composition ofthe present invention is used as a matrix resin, even if the resincontent of the prepreg is brought to less than 25% by weight, theobtained tubular molded article exhibits a crushing strength improvedmore than that of the conventional one. Accordingly, the tubular moldedarticle can be made light in weight with the properties includingcrushing strength satisfactorily maintained.

Particularly, when a tubular molded article is molded using a prepreg inwhich the flexural strength in a direction of 90° to the axes of thefibers, and the resin content of the prepreg and the elastic modulus ofthe carbon fibers satisfy the below-given relationship, the obtainedtubular molded article is good in the balance between the effect ofweight reduction and the physical properties including the crushingstrength:

flexural strength in a direction of 90° [MPa]≧X/the elastic modulus ofthe carbon fibers [GPa]

wherein X represents 100,000×the resin weight fraction of the prepreg

Next, the tubular molded article made of FRP in which theabove-described epoxy resin composition is used is described.

The tubular molded article of the present invention is a tubular moldedarticle excellent in crushing strength and flexural strength and isobtained by using the above-described epoxy resin composition for FRPfor the matrix resin of at least one FRP layer out of a plurality of FRPlayers.

This tubular molded article is generally obtained by winding layers ofprepregs around a mandrel and heating and pressing them. It is requiredthat at least one of these layers consist of the prepreg which is thethird mode of the present invention in order to obtain the desiredproperties. Further, if all of the layers consist of the prepregs of thepresent invention, excellent properties are obtained without anyproblems. However, since respective layers are generally allocatedrespective roles, it is not necessarily required that all the layersconsist of the prepregs of the present invention.

Further, it is possible to use layered prepregs made up of the prepregsof the present invention and conventional prepregs, which results inmore preferable physical properties in many cases. Further, the tubularmolded article can be obtained by a method wherein tow prepregs arewound to form layers. As the heating and pressing method used in moldingthe tubular molded article, compression molding in which a mold, such asa metal mold, is used, autoclave molding, vacuum bag molding, tapelapping molding, etc. can be mentioned by way of example, but the methodis not necessarily limited to them.

The epoxy resin composition for FRP of the present invention ispreferably such that when the epoxy resin composition is molded into thetubular molded article, the crushing strength of the tubular moldedarticle is 200 N or more, the tubular molded article having an innerdiameter of 10 mm, an outer diameter of 12 mm, and a volume content offibers of 60+1% and being prepared by impregnating carbon fibers havingan elastic modulus of 220 to 250 GPa with the epoxy resin compositionfor FRP to make unidirectional prepregs in which the carbon fiber arealweight is 150 g/m² and the content of the epoxy resin for FRP is 31% byweight and laminating the unidirectional prepregs so that the directionsof the fibers may be +45°/−45°/+45°/45°/0°/0°/0°. By defining thecrushing strength of the above tubular molded article as being 200 N ormore, the tubular molded article can be made light in weight bydecreasing the number of the laminated FRP layers. The crushing strengthof the tubular molded article is more preferably 240 N or more.

The epoxy resin composition for FRP of the present invention ispreferably such that when carbon fibers having an elastic modulus of 220to 250 GPa are impregnated with this epoxy resin composition for FRP tomake unidirectional prepregs in which the carbon fiber areal weight is150 g/m² and the content of the epoxy resin for FRP is 31% by weight andfifteen unidirectional prepregs thus made are laminated so that thedirections of the fibers may be zero degrees, thereby making aunidirectional laminate (2 mm in thickness), the flexural strength in adirection of 90° is 110 MPa or more. Thus, by making the flexuralstrength of the above unidirectional laminate in a direction of 90° tobe 110 MPa or more, the weight of the tubular molded article can be madelight by decreasing the number of the laminated layers of the FRPlayers. More preferably, the flexural strength of the aboveunidirectional laminate in a direction of 90° is 124 MPa or more andparticularly preferably 140 MPa or more.

EXAMPLES

Hereinbelow, the present invention is described more specifically withreference to Examples.

Abbreviations for compounds, and the test methods in the Examples are asfollows.

Component (A)

EP828: a bisphenol A-type epoxy resin, EPIKOTE 828 (epoxy equivalent:184-194; liquid at normal temperatures), manufactured by Yuka ShellEpoxy K. K.

EP1001: a bisphenol A-type epoxy resin, EPIKOTE 1001 (epoxy equivalent:450-500; solid at normal temperatures), manufactured by Yuka Shell EpoxyK. K.

EP1002: a bisphenol A-type epoxy resin, EPIKOTE 1002 (epoxy equivalent:600-700; solid at normal temperatures), manufactured by Yuka Shell EpoxyK. K.

EP1004: a bisphenol A-type epoxy resin, EPIKOTE 1004 (epoxy equivalent:875-975; solid at normal temperatures), manufactured by Yuka Shell EpoxyK. K.

Component (B)

XAC4151: an oxazolidone ring containing epoxy resin manufactured byAsahi-Ciba Limited

XAC4152: an oxazolidone ring containing epoxy resin manufactured byAsahi-Ciba Limited

Component (C)

PDMU: phenyldimethyl urea

DCMU: dichlorodimethyl urea

DICY: dicyandiamide

Component (D)

PY-50: a phenoxy resin, PHENOTOHTO, manufactured by Tohto Kasei Co.,Ltd.

VINYLEC E: a polyvinylformal manufactured by Chisso Corporation

VINYLEC K: a polyvinylformal manufactured by Chisso Corporation

Component (E)

N740: a phenol novolak-type epoxy resin, EPICLON N740 (semisolid atnormal temperatures), manufactured by Dainippon Ink and Chemicals Inc.

N775: a phenol novolak-type epoxy resin, EPICLON N775 (softening point:70-80° C.), manufactured by Dainippon Ink and Chemicals Inc.

Measurement of Viscosities

Use was made of a dynamic viscoelasticity measuring instrument RDA-700manufactured by Rheometric Scientific F. E. Ltd. The uncured epoxy resincomposition for FRP whose viscosity was to be measured was filledbetween two disk plates of 25 mm in diameter and the viscosity of theepoxy resin was measured under conditions in which the atmospherictemperature for the measurement was 60° C., the space between the diskplates was 0.5 mm, and the shear rate was 10 radians/sec.

G_(IC)

In accordance with ASTM-E399, the G_(IC) was measured by the compacttension method.

Evaluation of the Handleability of the Prepreg

The prepreg was subjected to a manual sensory test and was evaluatedbased on the following criteria:

∘: both the tack and the flexibility were good and winding around amandrel was quite easy.

Δ: flexibility was lacking and the winding around a mandrel was somewhatdifficult.

X: the tack was very strong and winding around a mandrel was difficult.

Measurement of Flexural Strength in a Direction of 90°

Carbon fibers having an elastic modulus of 220 to 250 GPa wereimpregnated with the epoxy resin composition for FRP to formunidirectional prepregs wherein the carbon fiber areal weight was 150g/m² and the content of the epoxy resin for FRP was 31% by weight.Fifteen layers of the thus made unidirectional prepregs were placed oneon top of the other with the direction of the fibers being at 0 degreesin order to mold a unidirectional laminate (2 mm in thickness). Thisunidirectional laminate was cut to obtain a test piece having a lengthof 60 mm in a direction of 90° to the direction of the fibers and awidth of 10 mm. The maximum load necessary to break the test piece wasmeasured under conditions in which the distance between the supports was32 mm, the tip diameter of the indenter was 3.2 mm, and the rate oftravel of the indenter was 2 mm/min and the flexural strength in adirection of 90° to the axes of the fibers was calculated.

More specifically, by using a universal testing machine, TENSILON,available from Orientec Corporation, the test piece measuring 60 mm inlength, 10 mm in width, and 2 mm in thickness was put to test under suchtest conditions that the L/D was 16 and the rate of travel of theindenter having a tip diameter of 3.2 mm was 2 mm/min, wherein L/Drepresents [the distance between the supports]/[the thickness of thetest piece].

Measurement of flexural Strength in the Direction of the Axes of theFibers

In the measurement of the flexural strength in the direction of the axesof the fibers, a test piece measuring 120 mm in length in the directionof the axes of the fibers, 10 mm in width, and 2 mm in thickness wasused and tested under such conditions that the rate of travel of theindenter having a tip diameter of 3.2 mm was 2 mm/min in the same way asin the method for measuring the flexural strength in a direction of 90°,except that L/D was 40.

Measurement of the Crushing Strength

Carbon fibers having an elastic modulus of 220 to 250 GPa wereimpregnated with the epoxy resin composition for FRP to formunidirectional prepregs wherein the carbon fiber areal weight was 150g/m² and the content of the epoxy resin for FRP was 31% by weight. Theunidirectional prepregs were placed one on top the other so that thedirections of the fibers might be +45°/−45°/+45°/−45°/0°/0°/0° to mold atubular molded article having an inner diameter of 10 mm, an outerdiameter of 12 mm and a volume content of fibers of 60±1%. The tubularmolded article was cut into a 10 mm length to obtain a test piece. Aload was applied to the test piece by using an indenter and the maximumload required until the test piece broke with the rate of travel of theindenter being 5 mm/min was measured, the maximum load being designatedthe crushing strength.

More specifically, by using a universal testing machine, TENSILON,available from Orientec Corporation, a load was applied to each of eighttest pieces radially by the indenter to smash it and the maximum loadrequired until it was broken was measured. The average value of theeight measurements was designated the crushing strength.

Four-Point Flexural Test of FRP Tubular Molded Articles

As a test piece, a tubular molded article was prepared in which, inorder to prevent stresses from being concentrated, aluminum rings havingan inner diameter of 11.5 mm, a wall thickness of 2 mm, and a width of10 mm were mounted on parts where supports and indenters would come incontact with the tubular molded article. Using a universal testingmachine, TENSILON, available from Orientec Corporation, a load wasapplied to each of such test pieces under such conditions that thedistance between the movable indenters was 500 mm, the distance betweenthe fixed indenters (supports) was 150 mm, and the rate of travel of theindenter was 15 mm/min to measure the flexural strength. The averagevalue of six such measurements was designated the flexural strength.Both the measurement of the crushing strength and the four-pointflexural test were carried out under atmospheric conditions at 21° C.and 50% RH.

Glass Transition Temperature (Tg) of the Cured Resin

By using a dynamic viscoelasticity measuring instrument, RDA-700,available from Rheometric Scientific F. E. Ltd., a shearing force wasapplied to a test piece 60 mm in length, 12 mm in width, and 2 mm inwidth at a rate of 10 radians/sec with the temperature increased at 5°C./STEP and the temperature dependence of the storage modulus wasmeasured. The intersection of the tangent of the storage modulus curveto the glass state region with the tangent to the transition region wasfound as the glass transition temperature.

Formation of a Shaft for the Measurement of the Torsional Strength

Each of the shafts for golf clubs was made using the above prepregs inthe following manner.

First, the prepregs were cut in such a manner that when the prepreg waswound around a tapered mandrel whose small-diameter part had an outerdiameter of 4.6 mm, whose large-diameter part had an outer diameter of14.3 mm, and whose length was 1,500 mm, with the direction of the fibersforming an angle of +45°, two layers would be formed at the oppositeends, and when the prepreg was wound around it with the direction of thefibers forming an angle of −45°, the same formation would be secured.Then these prepregs were stuck together with the directions of thefibers orthogonal to each other. The laminated prepreg was wound aroundthe mandrel to form an angle layer. Then, a straight layer was formed bywinding three of the prepregs on the above angle layer so that the aboveangle might be 0°. Then after a polypropylene tape having a width of 20mm and a thickness of 30 μm was wound thereon with a pitch of 2 mm beingsecured, it was placed in a curing oven, where it was heated at atemperature of 145° C. for 240 min to cure the resin. After the curing,the core was removed, the polypropylene tape was torn off, a length of10 mm was cut off from the small-diameter part and from thelarge-diameter part to obtain a shaft for a golf club for the test.

Measurement of the Torsional Strength

The torsional strength of each of the shafts for golf clubs made in theabove manner was measured. The measurement was carried out in accordancewith the torsional test of the qualification standard and standardcertification method of shafts for golf clubs (5 San No. 2087 (Oct. 4,1993) approved by Minister of Japanese Ministry of International Trade &Industry) settled by Product Safety Society. First, by using a “5KNuniversal tester” (manufactured by Mechatronics Engineering Inc.), thesmall-diameter part of the test golf club shaft was fixed, torque wasapplied to the large-diameter part, and when the shaft broke due to thetorsion, this torsion was designated the torsional strength, and itstorsional angle was designated the break angle. The product of thetorsional strength and the break angle was expressed as the torsionalbreaking energy.

Examples 1 to 11 and Comparative Examples 1 to 5

Epoxy resin compositions having the formulations (the values indicateparts by weight) shown in Tables 1 and 2 were prepared and each of themwas coated to a release paper. Unidirectionally arranged carbon fibers(TR30G-12L manufactured by Mitsubishi Rayon Co., Ltd.) were placed onthe epoxy resin composition to allow them to be impregnated with theepoxy resin composition thereby obtaining a unidirectional prepregwherein the carbon fiber areal weight was 150 g/m² and the resin contentwas 31% by weight. The viscosities of the used epoxy resin compositionsand the results of the evaluation of the handleability of the obtainedprepregs are also shown in Tables 1 and 2.

Then, the obtained prepregs were laminated with the directions of thecarbon fiber arranged and each of the obtained laminates was subjectedto vacuum bag molding under curing conditions at 130° C. for 1 hour toobtain an FRP unidirectional molded article having the carbon fibers asreinforcing fibers (hereinafter referred to as unidirectional moldedarticle). With respect to the obtained unidirectional molded articles, aflexural test in a direction of the axes of the fibers and in adirection at right angles to the axes of the fibers, and measurement ofthe glass transition temperature were carried out. The results of themeasurements are also shown in Tables 1 and 2.

Further, the obtained prepregs were stuck together with the directionsof the fibers orthogonal to each other to form laminated prepreg eachhaving two layers. Then, each laminated prepreg was wounded two timesaround a mandrel having a diameter of 10 mm so that the directions ofthe fibers might be at ±45 degrees with respect to the length of themandrel to form four prepreg layers with the two layers having +45degrees and the two layers having −45 degrees arranged orthogonally toeach other. Then, further, the prepreg was wound three times around themandrel with the direction of the fibers in line with the length of themandrel to form three 0-degree layers. The molding of the thus formedlaminate was carried out by taping polypropylene molding tape (having athickness of 30 μm and a width of 15 mm) to the surface with the tensionbeing 6.5 kg/15 mm and the pitch being 3 mm and heating in a curing ovenat 130° C. for 1 hour. After the curing, the mandrel was withdrawn andthe tape was unwound to obtain a tubular molded article having a wallthickness of 1.0 mm and carbon fibers as reinforcing fibers (hereinafterreferred to as tubular molded article). With respect to the thusobtained tubular molded articles, the crushing test was carried out. Theresults are shown in Tables 1 and 2.

In passing, unidirectional molded articles and tubular molded articlesincluding those in the following Examples and Comparative Examples wereall prepared so as to have a volume content of carbon fibers of 60±1%unless otherwise stated.

TABLE 1 Example 1 2 3 4 5 Component (A) EP828 20 30 20 20 30 EP1001 5030 30 EP1002 30 40 EP1004 Component (B) XAC4151 30 40 50 XAC4152 50 30Component (C) DICY 5 5 5 5 5 DCMU 4 4 4 4 4 PDMU Component (E) N740 N775Viscosity (poises, 60° C.) 1,700 758 702 2,040 898 G_(IC) of the resin(J/m²) 640 690 700 710 600 Handleability of the prepreg ∘ ∘ ∘ ∘ ∘ Carbonfibers TR30G TR30G TR30G TR30G TR30G Flexural strength of theunidirectional In the 1,637 1,627 1,646 1,637 1,656 molded article (MPa)direction of fibers In a direction 131 133 137 127 132 of 90° Glasstransition temperature (° C.) 122 126 127 125 120 Crushing strength ofthe tubular molded article (N) 235 245 255 245 245 Torsional strength (N· m) 13.1 13.1 13.2 13.0 13.3 Break angle (°) 101 101 102 100 100Torsional breaking energy (N · m°) 1,323 1,323 1,346 1,300 1,330 Example6 7 8 9 10 11 Component (A) EP828 50 30 50 30 40 40 EP1001 EP1002 40 5030 EP1004 30 30 Component (B) XAC4151 20 30 20 70 10 10 XAC4152Component (C) DICY 5 5 5 5 5 5 DCMU 4 4 4 4 PDMU 2 2 Component (E) N740N775 20 Viscosity (poises, 60° C.) 1,600 748 1,330 745 694 600 G_(IC) ofthe resin (J/m²) 510 610 500 720 450 470 Handleability of the prepreg ∘∘ ∘ ∘ ∘ ∘ Carbon fibers TR30G TR30G TR30G TR30G TR30G TR30G Flexuralstrength of the unidirectional In the 1,646 1,676 1,666 1,715 1,6371,666 molded article (MPa) direction of fibers In a direction 127 137132 118 120 131 of 90° Glass transition temperature (° C.) 122 120 122130 112 132 Crushing strength of the tubular molded article (N) 225 255235 206 216 206 Torsional strength (N · m) 13.0 13.2 13.1 12.0 12.1 13.1Break angle (°) 100 102 101 98 98 101 Torsional breaking energy (N · m°)1,300 1,346 1,346 1,176 1,186 1,323

TABLE 2 Comparative Example 1 2 3 4 5 Component (A) EP828 5 5 60 3EP1001 65 65 47 EP1002 50 EP1004 Component (B) XAC4151 XAC4152 40 50Component (C) DICY 5 5 5 5 5 DCMU 4 4 4 4 PDMU 2 Component (E) N740 3050 30 N775 Viscosity (poises, 60° C.) 901 775 748 93 5,390 G_(IC) of theresin (J/m²) 320 280 290 670 730 Handleability of the prepreg ∘ ∘ ∘ x ΔCarbon fibers TR30G TR30G TR30G TR30G TR30G Flexural strength of theunidirectional In the 1,637 1,646 1,646 1,686 1,646 molded article (MPa)direction of fibers In a direction 115 111 123 137 73.5 of 90° Glasstransition temperature (° C.) 122 125 123 132 124 Crushing strength ofthe tubular molded article (N) 186 176 176 255 167 Torsional strength (N· m) 11.8 11.6 12.1 13.2 7.5 Break angle (°) 96 95 98 102 55 Torsionalbreaking energy (N · m°) 1,133 1,102 1,186 1,346 413

Examples 12 to 14 and Comparative Examples 6 to 8

Prepared in the same way as in Example 1, except that epoxy resincompositions having the formulations shown in Tables 3 and 4 wereprepared and HR40-12M manufactured by Mitsubishi Rayon Co., Ltd. wereused as the carbon fibers. The handleability of the prepregs and theproperties of the unidirectional molded articles and tubular moldedarticles were evaluated. The results are also shown in Tables 3 and 4.

TABLE 3 Example 12 13 14 Component (A) EP828 20 20 30 EP1001 50 EP100230 40 EP1004 Component (B) XAC4151 30 30 XAC4152 50 Component (C) DICY 55 5 DCMU 4 4 PDMU 2 Component (E) N740 Viscosity (poises, 60° C.) 1,7002,040 748 G_(IC) of the resin (J/m²) 640 710 610 Handleability of theprepreg ∘ ∘ ∘ Carbon fibers HR40 HR40 HR40 Flexural strength of theunidirectional In the 1,578 1,617 1,617 molded article (MPa) directionof fibers In a direction 99 98 101 of 90° Glass transition temperature(° C.) 122 125 120 Crushing strength of the tubular molded article (N)186 206 196 Torsional strength (N · m) 9.9 9.9 9.9 Break angle (°) 76 7677 Torsional breaking energy (N · m°) 752 752 762

TABLE 4 Comparative Example 6 7 8 Component (A) EP828 5 5 EP1001 65 65EP1002 50 EP1004 Component (B) XAC4151 XAC4152 Component (C) DICY 5 5 5DCMU 4 4 PDMU 2 Component (E) N740 30 50 30 Viscosity (poises, 60° C.)901 775 748 G_(IC) of the resin (J/m²) 320 280 290 Handleability of theprepreg ∘ ∘ ∘ Carbon fibers HR40 HR40 HR40 Flexural strength of theunidirectional In the 1,588 1,578 1,568 molded article (MPa) directionof fibers In a direction 80 79 81 of 90° Glass transition temperature (°C.) 122 125 123 Crushing strength of the tubular molded article (N) 137127 132 Torsional strength (N · m) 8.2 8.1 8.2 Break angle (°) 67 66 67Torsional breaking energy (N · m°) 549 535 549

Examples 15 to 38 and Comparative Examples 9 to 20

Prepared in the same way as in Example 1, except that epoxy resincompositions having the formulations shown in Tables 5 to 8 wereprepared and TR30S-12L manufactured by Mitsubishi Rayon Co., Ltd. wereused as the carbon fibers. The handleability of the prepregs and theproperties of the unidirectional molded articles and tubular moldedarticles were evaluated. The results are also shown in Tables 5 to 8.

TABLE 5 Example 15 16 17 18 19 20 Component (A) EP828 30 30 30 55 45 35EP1001 EP1002 25 35 45 Component (B) XAC4151 XAC4152 70 70 70 20 20 20Component (C) DICY 4 4 4 4 4 4 DCMU 4 4 4 4 4 4 PDMU Component (D) YP-506 12 18 8 8 8 Component (E) N740 Viscosity (poises, 60° C.) 1,100 1,5003,500 1,500 2,800 4,900 G_(IC) of the resin (J/m²) 720 730 750 530 550540 Handleability of the prepreg ∘ ∘ ∘ ∘ ∘ ∘ Carbon fibers TR30S TR30STR30S TR30S TR30S TR30S Flexural strength of the unidirectional In the1,705 1,686 1,676 1,656 1,666 1,656 molded article (MPa) direction offibers In a direction 140 138 133 135 137 136 of 90° Glass transitiontemperature (° C.) 130 129 129 124 123 121 Crushing strength of thetubular molded article (N) 254.8 245 245 255 255 255 Torsional strength(N · m) 13.7 13.4 13.3 13.3 13.4 13.4 Break angle (°) 104 102 101 101101 102 Torsional breaking energy (N · m°) 1,394 1,367 1,343 1,343 1,3531,367 Example 21 22 23 24 25 26 Component (A) EP828 20 20 50 40 40 40EP1001 60 30 EP1002 20 40 40 Component (B) XAC4151 30 30 XAC4152 20 5020 20 Component (C) DICY 4 4 4 4 4 4 DCMU 4 4 4 4 PDMU 4 4 Component (D)YP-50 8 8 8 8 8 10 Component (E) N740 30 Viscosity (poises, 60° C.)2,500 3,300 2,000 2,900 2,600 2,100 G_(IC) of the resin (J/m²) 520 630610 540 530 490 Handleability of the prepreg ∘ ∘ ∘ ∘ ∘ ∘ Carbon fibersTR30S TR30S TR30S TR30S TR30S TR30S Flexural strength of theunidirectional In the 1,676 1,715 1,705 1,695 1,676 1,646 molded article(MPa) direction of fibers In a direction 134 139 141 138 137 136 of 90°Glass transition temperature (° C.) 120 126 127 124 123 133 Crushingstrength of the tubular molded article (N) 245 245 255 255 255 245Torsional strength (N · m) 13.3 13.4 13.7 13.4 13.3 13.3 Break angle (°)101 102 104 102 102 101 Torsional breaking energy (N · m°) 1,343 1,3671,425 1,367 1,357 1,343

TABLE 6 Comparative Example 9 10 11 12 13 14 Component (A) EP828 25 8010 10 10 10 EP1001 60 60 40 20 EP1002 55 Component (B) XAC4151 XAC415220 20 Component (C) DICY 4 4 4 4 4 4 DCMU 4 4 4 4 4 4 PDMU Component (D)YP-50 8 2 6 12 6 6 Component (E) N740 30 30 50 70 Viscosity (poises, 60°C.) 6,400 90 2,000 2,800 2,400 2,100 G_(IC) of the resin (J/m²) 550 510300 350 270 260 Handleability of the prepreg Δ x ∘ ∘ ∘ ∘ Carbon fibersTR30S TR30S TR30S TR30S TR30S TR30S Flexural strength of theunidirectional In the 1,637 1,685 1,676 1,656 1,656 1,627 molded article(MPa) direction of fibers In a direction 93 129 108 103 98 70 of 90°Glass transition temperature (° C.) 120 132 125 123 126 132 Crushingstrength of the tubular molded article (N) 186 196 176 176 186 167Torsional strength (N · m) 9.8 12.8 11.4 10.5 10.0 7.3 Break angle (°)77 99 95 85 75 53 Torsional breaking energy (N · m°) 755 1,267 1,083 893750 387

TABLE 7 Example 27 28 29 30 31 32 Component (A) EP828 30 30 30 50 40 30EP1001 EP1002 30 40 50 Component (B) XAC4151 XAC4152 70 70 70 20 20 20Component (C) DICY 4 4 4 4 4 4 DCMU 4 4 4 4 4 4 PDMU Component (D)VINYLEC E 3 6 9 4 4 4 VINYLEC K Component (E) N740 Viscosity (poises,60° C.) 980 1,400 3,000 1,200 2,500 4,900 G_(IC) of the resin (J/m²) 730730 740 510 570 550 Handleability of the prepreg ∘ ∘ ∘ ∘ ∘ ∘ Carbonfibers TR30S TR30S TR30S TR30S TR30S TR30S Flexural strength of theunidirectional In the 1,715 1,695 1,676 1,646 1,637 1,646 molded article(MPa) direction of fibers In a direction 144 143 149 145 140 137 of 90°Glass transition temperature (° C.) 129 130 128 126 124 121 Crushingstrength of the tubular molded article (N) 265 255 265 274 265 255Torsional strength (N · m) 13.7 13.5 13.8 13.7 13.8 13.4 Break angle (°)103 103 104 102 105 101 Torsional breaking energy (N · m°) 1,411 1,3911,435 1,397 1,449 1,353 Example 33 34 35 36 37 38 Component (A) EP828 2020 50 40 40 40 EP1001 60 30 EP1002 20 40 40 Component (B) XAC4151 30 30XAC4152 20 50 20 20 Component (C) DICY 4 4 4 4 4 4 DCMU 4 4 4 4 PDMU 4 4Component (D) VINYLEC E 4 4 4 4 5 VINYLEC K 5 Component (E) N740 30Viscosity (poises, 60° C.) 2,200 3,100 1,800 2,700 2,500 2,000 G_(IC) ofthe resin (J/m²) 520 640 600 540 540 500 Handleability of the prepreg ∘∘ ∘ ∘ ∘ ∘ Carbon fibers TR30S TR30S TR30S TR30S TR30S TR30S Flexuralstrength of the unidirectional In the 1,656 1,705 1,715 1,705 1,6951,646 molded article (MPa) direction of fibers In a direction 141 146139 138 136 134 of 90° Glass transition temperature (° C.) 120 125 127123 123 133 Crushing strength of the tubular molded article (N) 265 265265 265 255 245 Torsional strength (N · m) 14.1 13.8 13.5 13.5 13.4 13.3Break angle (°) 107 104 102 102 101 101 Torsional breaking energy (N ·m°) 1,509 1,435 1,377 1,377 1,353 1,343

TABLE 8 Comparative Example 15 16 17 18 19 20 Component (A) EP828 25 8010 10 10 10 EP1001 60 60 40 20 EP1002 55 Component (B) XAC4151 XAC415220 20 Component (C) DICY 4 4 4 4 4 4 DCMU 4 4 4 4 4 4 PDMU Component (D)VINYLEC E 4 2 3 6 3 3 VINYLEC K Component (E) N740 30 30 50 70 Viscosity(poises, 60° C.) 6,200 90 1,800 2,500 2,200 1,800 G_(IC) of the resin(J/m²) 530 520 290 360 270 240 Handleability of the prepreg Δ x ∘ ∘ ∘ ∘Carbon fibers TR30S TR30S TR30S TR30S TR30S TR30S Flexural strength ofthe unidirectional In the 1,656 1,705 1,666 1,666 1,656 1,637 moldedarticle (MPa) direction of fibers In a direction 98 131 113 108 103 78of 90° Glass transition temperature (° C.) 121 133 124 123 127 134Crushing strength of the tubular molded article (N) 196 216 206 196 196206 Torsional strength (N · m) 10.1 13 11.5 11.4 10.8 7.5 Break angle(°) 82 100 95 94 85 56 Torsional breaking energy (N · m°) 828 1,3001,420 1,072 918 420

Examples 39 to 41 and Comparative Examples 21 to 23

Prepared in the same way as in Example 1, except that the carbon fibersand the epoxy resin compositions shown in Tables 9 and 10 were used. Theflexural strength in a direction of 90° of unidirectional moldedarticles and the crushing strength of tubular molded articles wereevaluated. The results are also shown in Tables 9 and 10.

TABLE 9 Example 30 39 40 41 Carbon fibers TR30S MR40 HR40 HS40 Elasticmodulus of the carbon fibers (GPa) 235 294 392 451 Epoxy resincomposition Ex. 30 Ex. 30 Ex. 30 Ex. 30 Resin content (wt. %) 30 30 3030 25,000/the elastic modulus of the carbon fibers 107 85 64 56 Flexuralstrength in a direction of 90° (MPa) 145 124 103 91 Crushing strength ofthe tubular molded article (N) 274 255 221 211 Torsional strength (N ·m) 13.7 12.3 10.2 9.0 Break angle (°) 102 93 79 70 Torsional breakingenergy (N · m°) 1,397 1,144 806 630

TABLE 10 Comparative Example 19 21 22 23 Carbon fibers TR30S MR40 HR40HS40 Elastic modulus of the carbon fibers (GPa) 235 294 392 451 Epoxyresin composition Comp. Comp. Comp. Comp. Ex. 19 Ex. 19 Ex. 19 Ex. 19Resin content (wt. %) 30 30 30 30 25,000/the elastic modulus of thecarbon fibers 107 85 64 56 Flexural strength in a direction of 90° (MPa)103 80 59 54 Crushing strength of the tubular molded article (N) 196 162136 130 Torsional strength (N · m) 10.8 8.8 7.0 6.2 Break angle (°) 8568 53 48 Torsional breaking energy (N · m°) 918 598 371 298

Example 42 and Comparative Example 24

Prepared in the same way as in Example 1, except that HR40-12Mmanufactured by Mitsubishi Rayon Co., Ltd. were used as the carbonfibers and the compositions of Example 30 and Comparative Example 19were used as the matrix resin. The flexural strength in a direction of90° of unidirectional molded articles and the crushing strength oftubular molded articles were evaluated. The results are shown in Table11.

TABLE 11 Example Comparative Example 40 42 22 24 Carbon fibers HR40 HR40HR40 HR40 Elastic modulus of the carbon fibers (GPa) 392 392 392 392Epoxy resin composition Ex. 30 Ex. 30 Comp. Ex. 19 Comp. Ex. 19 Resincontent (wt. %) 30 20 30 20 100,000 × the resin fraction of theprepreg/the 77 51 77 51 elastic modulus of the carbon fibers Flexuralstrength in a direction of 90° (MPa) 103 68 59 46 Crushing strength ofthe tubular molded article (N) 221 147 136 98

Examples 43 to 48 and Comparative Examples 25 and 26

Using the epoxy resin compositions prepared in Example 23 andComparative Example 13 and the following two types of carbon fibers,four types of high-weight prepregs having a prepreg areal weight of 180g/m² and a resin content of 30% by weight were produced.

[Used Carbon Fibers]

TR30S-12L: manufactured by Mitsubishi Rayon Co., Ltd.; has an elasticmodulus of 235 GPa

MR40-12M: manufactured by Mitsubishi Rayon Co., Ltd.; has an elasticmodulus of 294 GPa

Further, using the same two types of epoxy resin compositions andTR30-3L, two types of low-weight prepregs having a prepreg areal weightof 48 g/m² and a resin content of 40% by weight were produced.

Then the obtained high-weight prepregs and low-weight prepregs werestuck together such that the directions of the carbon fibers wereorthogonal to each other, thereby obtaining laminated prepregs. Theobtained prepregs were good prepregs wherein there were no defectivelybonded parts and evaluation by touch showed that the surface was smooth.Each prepreg was wound around a mandrel having a diameter of 10 mm fourtimes (equivalent to 8 layers) with the low-weight prepreg inside sothat the circumferential direction might be reinforced. Then moldingthereof was carried out in the same way for the tubular molded articlein Example 1, thereby obtaining a tubular molded article having a lengthof 600 mm, a wall thickness of 0.58 mm, and a weight of 18 g. Theaverage volume content of the carbon fibers of this tubular moldedarticle was 56%.

The flexural test of the obtained molded articles was carried out. Theresults are shown in Tables 12 and 13.

TABLE 12 Example 43 44 45 46 Axial reinforcing layer Carbon fibers TR30STR30S TR30S MR40 Epoxy resin composition Ex. 23 Comp. Ex. 23 Ex. 23 Ex.13 Resin content (wt. %) 30 30 30 30 Circumferential reinforcing layerCarbon fibers TR30 TR30 TR30 TR30 Epoxy resin composition Ex. 23 Ex. 23Comp. Ex. 23 Ex. 13 Resin content (wt. %) 40 40 40 40 Four-pointflexural properties Strength (MPa) 1,216 1,193 1,193 1,298 Elasticmodulus (GPa) 131 131 131 164 Breaking strain (%) 1.19 1.28 1.28 1.19

TABLE 13 Comparative Example Example 47 48 25 26 Axial reinforcing layerCarbon fibers MR40 MR40 TR30S MR40 Epoxy resin composition Comp. Ex. 23Comp. Comp. Ex. 13 Ex. 13 Ex. 13 Resin content (wt. %) 30 30 30 30Circumferential reinforcing layer Carbon fibers TR30 TR30 TR30 TR30Epoxy resin composition Ex. 23 Comp. Comp. Comp. Ex. 13 Ex. 13 Ex. 13Resin content (wt. %) 40 40 40 40 Four-point flexural propertiesStrength (MPa) 1,271 1,199 1,173 1,250 Elastic modulus (GPa) 163 163 127155 Breaking strain (%) 1.15 1.01 1.22 1.14

Examples 49 to 53 and Comparative Examples 27 and 28

Tubular molded articles were obtained and evaluated in the same manneras in Examples 43 to 48 and Comparative Examples 27 and 28, except thatthe epoxy resin compositions prepared in Example 30 and ComparativeExample 19 were used.

The results are shown in Tables 14 and 15.

TABLE 14 Example 49 50 51 52 53 Axial reinforcing layer Carbon fibersTR30S TR30S TR30S MR40 MR40 Epoxy resin composition Ex. 30 Comp. Ex. 30Ex. 30 Comp. Ex. 19 Ex. 19 Resin content (wt. %) 30 30 30 30 30Circumferential reinforcing layer Carbon fibers TR30 TR30 TR30 TR30 TR30Epoxy resin composition Ex. 30 Ex. 30 Comp. Ex. 30 Ex. 30 Ex. 19 Resincontent (wt. %) 40 40 40 40 40 Four-point flexural properties Strength(MPa) 1,231 1,213 1,203 1,308 1,281 Elastic modulus (GPa) 132 132 132165 164 Breaking strain (%) 1.29 1.29 1.29 1.20 1.16

TABLE 15 Comparative Example 27 28 Axial reinforcing layer Carbon fibersTR30S MR40 Epoxy resin composition Comp. Comp. Ex. 19 Ex. 19 Resincontent (wt. %) 30 30 Circumferential reinforcing layer Carbon fibersTR30 TR30 Epoxy resin composition Comp. Comp. Ex. 19 Ex. 19 Resincontent (wt. %) 40 40 Four-point flexural properties Strength (MPa)1,173 1,250 Elastic modulus (GPa) 127 155 Breaking strain (%) 1.22 1.14

Examples 53 to 58 and Comparative Examples 29 and 30

Tubular molded articles were obtained and evaluated in the same manneras in Examples 43 to 48 and Comparative Examples 27 and 28, except thatinstead of the low-weight prepregs constituting the inside of thetubular molded articles, a glass scrim cloth prepreg manufactured byNitto Boseki Co., Ltd. (Product No.: WP (A) 03 104; areal weight: 24.5g/m²; epoxy resin content: 26 wt. %) was used.

The results are shown in Tables 16 and 17.

TABLE 16 Example 55 56 57 58 Prepreg Carbon fibers TR30S MR40 TR30S MR40Epoxy resin Ex. 23 Ex. 23 Ex. 30 Ex. 30 composition Physical Crushing220 151 230 165 properties of strength (N) the tubular Breaking 135 78.7136 78.9 molded article strength (MPa) Elastic modulus 7,281 6,840 7,2916,899 (MPa) Breaking strain 1.86 1.25 1.88 1.14 (%)

TABLE 17 Comparative Example 29 30 Prepreg Carbon fibers TR30S MR40Epoxy resin composition Comp. Comp. Ex. 13 Ex. 13 Physical Crushingstrength (N) 172 107 properties of Breaking strength (MPa) 86.2 48.8 thetubular Elastic modulus (MPa) 7,193 5,762 molded article Breaking strain(%) 1.20 0.87

Examples 59 to 61

The epoxy resin compositions in Examples 1, 5 and 9 were coated on tosheets of release paper and unidirectionally arranged carbon fibers(TR30G-12L manufactured by Mitsubishi Rayon Co., Ltd.) were impregnatedtherewith with the opposite sides of the arranged carbon fibers beingsandwiched between the sheets, thereby obtaining unidirectional prepregshaving a carbon fiber areal weight of 150 g/m² and a resin content of31% by weight.

The results of the evaluation are shown in Table 18.

TABLE 18 Example 50 60 61 Component (A) EP828 20 30 30 EP1001 50 EP100240 EP1004 Component (B) XAC4151 30 70 XAC4152 30 Component (C) DICY 5 55 DCMU 4 4 4 PDMU Component (E) N740 Viscosity (poises, 60° C.) 1,700898 745 G_(IC) of the resin (J/m²) 640 600 720 Handleability of theprepreg ∘ ∘ ∘ Carbon fibers TR30G TR30G TR30G Flexural strength of theunidirectional In the 1,640 1,662 1,705 molded article (MPa) directionof fibers In a direction 141 143 138 of 90° Glass transition temperature(° C.) 122 132 130 Crushing strength of the tubular molded article (N)255 260 250 Torsional strength (N · m) 13.6 13.8 13.3 Break angle (°)104 106 103 Torsional breaking energy (N · m°) 1,414 1,463 1,370 *1 *2*3 *1 the same resin composition as that in Example 1 *2 the same resincomposition as that in Example 5 *3 the same resin composition as thatin Example 9

Industrial Applicability

The epoxy resin composition for FRP of the present invention is betterin adhesion to reinforcing fibers than conventional mainstream epoxyresin compositions whose major compositions are a bisphenol A-type epoxyresin and a phenolic novolak-type epoxy resin, and the prepreg thereofis quite excellent in handleability.

Further, since the FRP tubular molded article in which this epoxy resincomposition is used is excellent in physical flexural properties andphysical crushing properties, fishing rods and shafts of golf clubsobtained using the FRP tubular molded article can be made light inweight.

What is claimed is:
 1. An epoxy resin composition, consistingessentially of (A) a bisphenol A epoxy resin, (B) an epoxy resin havingoxazolidone rigs and having no isocyanate groups, (C) a curing agent,and (D) a thermoplastic resin which is soluble in a mixture of saidbisphenol A epoxy resin (A) and said epoxy resin (B), said epoxy resin(B) being an epoxy resin having a structure represented by the followingformula (2):

wherein R each independently represents a hydrogen atom or a methylgroup, R₁ to R₄ each independently represent a halogen atom, a hydrogenatom, or an alkyl group having 1 to 4 carbon atoms, R₅ to R₈ eachindependently represent a hydrogen atom or an alkyl group having 1 to 4carbon atoms, and R₉ represents the following formula (3) or (4):

wherein R′₁ to R′₄ each independently represent a hydrogen atom or analkyl group having 1 to 4 on atoms;

wherein R′₁ to R′₈ each independently represent a hydrogen atom or analkyl group having 1 to 4 carbon atoms and R′₉ represents a single bond,—CH₂—, —C(CH₃)₂—, —SO₂—, —SO—, —S—, or —O—, and wherein said bisphenol Aepoxy resin (A) is a mixture of a bisphenol A epoxy resin which has anepoxy equivalent of 300 or less and is liquid or semisolid at normaltemperatures and a bisphenol A epoxy resin which has an epoxy equivalentof 400 or more and is solid at normal temperatures.
 2. The epoxy resincomposition as claimed in claim 1, wherein the viscosity of said epoxyresin composition of (A)+(B)+(C)+(D) is 100 to 5,000 poises at 60° C. 3.The epoxy resin composition as claimed in claim 1, wherein saidthemoplastic resin (D) is a phenoxy resin and/or a polyvinylformal. 4.The epoxy resin composition as claimed in claim 1, further comprising(E) other epoxy resin in an amount of 3 to 20% by weight based on thetotal of the epoxy resin components comprising the bisphenol A epoxyresin (A), the epoxy resin (B), and the other epoxy resin (E).
 5. Theepoxy resin composition as claimed in claim 1, wherein said bisphenol Aepoxy resin which has an epoxy equivalent of 300 or less and is liquidor semisolid at normal temperatures is contained in an amount of 25 to65% by weight based on the bisphenol A epoxy resin (A), and the epoxyresin (B) is contained in an amount of 20 to 50% by weight based on amixture of the bisphenol A epoxy resin (A) and the epoxy resin (B). 6.The epoxy resin composition as claimed in claim 1, wherein thecomposition ratio by weight of the bisphenol A epoxy resin (A), theepoxy resin (B), and the thermoplastic resin soluble in a mixture ofthem (D) is such that (A)/(B)=from 15/1 to 1/5 and (D)/[(A)+(B)]=from1/100 to 30/100.
 7. The epoxy resin composition as claimed in claim 4,wherein the sum of the amount of the epoxy resin (B) added and theamount of the other epoxy resin (E) added is 20 to 50% by weight basedon the total of the epoxy resin components comprising the bisphenol Aepoxy resin (A), the epoxy resin (B), and the other epoxy resin (E) andthe composition ratio by weight of the epoxy resin (B) to the otherepoxy resin (E) is in the range of from 1/3 to 4/1.
 8. The epoxy resincomposition as claimed in claim 1, wherein the critical strain energyrelease rate G_(IC) is 400 J/m² or more.
 9. The epoxy resin compositionas claimed in claim 4, wherein the critical strain energy release rateG_(IC) is 400 J/m² or more.
 10. The epoxy resin composition as claimedin claim 1, wherein said curing agent (C) is a mixture of dicyandiamideand a urea compound.
 11. The epoxy resin composition as claimed in claim4, wherein said curing agent (C) is a mixture of dicyandiamide and aurea compound.
 12. A prepreg, comprising a sheet of reinforcing fibersimpregnated with the epoxy resin composition as claimed in claim
 1. 13.A prepreg, comprising a sheet of reinforcing fibers impregnated with theepoxy resin composition as claimed in claim
 4. 14. A prepreg, comprisinga sheet of reinforcing fibers impregnated with the epoxy resincomposition as claimed in claim
 10. 15. A prepreg, comprising a sheet ofreinforcing fibers impregnated with the epoxy resin composition asclaimed in claim
 11. 16. A tubular molded article having a plurality offiber reinforced plastic layers, wherein the matrix resin compositionused in at least one of sad layers is the epoxy resin composition asclaimed in claim
 1. 17. A tubular molded article having a plurality offiber reinforced plastic layers, wherein the matrix resin compositionused in at least one of said layers is the epoxy resin composition asclaimed in claim
 4. 18. A tubular molded article having a plurality offiber reinforced plastic layers, wherein the matrix resin compositionused in at least one of said layers is the epoxy resin composition asclaimed in claim
 10. 19. A tubular molded article having a plurality offiber reinforced plastic layers, wherein the matrix resin compositionused in at least one of said layers is the epoxy resin composition asclaimed in claim
 11. 20. An epoxy resin composition according to claim1, wherein the crushing strength will be 200 N or more when it is moldedinto a tubular shape.
 21. An epoxy resin composition according to claim1, wherein the crushing strength will be 240 N or more when it is moldedinto a tubular shape.
 22. An epoxy resin composition according to claim1, wherein the flexural strength in the direction of 90° is 100 MPa ormore when it is formed into a unidirectional laminate.
 23. An epoxyresin composition according to claim 1, wherein the flexural strength inthe direction of 90° is 125 MPa or more when it is formed into aunidirectional laminate.
 24. The epoxy resin composition as claimed inclaim 1, wherein said bisphenol A epoxy resin having an epoxy resinequivalent of 300 or less is contained in an amount of 25 to 65% byweight in the component (A).
 25. The epoxy resin composition as claimedin claim 1, wherein said viscosity is 300 to 3000 poises at 60° C. 26.The epoxy resin composition as claimed in claim 6, wherein thecomposition ratio by weight of the bisphenol A epoxy resin (A), theepoxy resin (B), and the thermoplastic resin soluble in a mixture ofthem (D) is such that (A)/(B)=from 10/1 to 1/3 and (D)/[(A)+(B)]=from2/100 to 20/100.